(from John R. Levison, Filled with the Spirit, Eerdmans, 2010).
Truth has always been a rare commodity among humanity. As part of the Fall we are constantly battling what is true and what is false, what edifies and what destroys, what reveals and what deceives. When Jesus tells his disciples that a 'spirit of truth' is to come upon them, he emphasizes the arrival of restoration from such a fallen state. Thus, he informs the world that there is something coming which will be unfamiliar and odd - pure truth in the midst of a world of muddied deception.
The world cannot receive this spirit of truth, he says to us. But it is coming nonetheless to those who follow after him. This can only lead to a significant break between those who are sprited-people and those who align their hearts to the stuff of earth. Of course, we will not see that the coming of this spirit of truth leads to a geographic distinction between these two people. They will walk among each other and interact in this life.
And so, Jesus tells us also that his followers - who are these spirit-of-truth-people - will be in this world, even though they will not be of this world. Their stuff will not be the stuff of earth, but will reflect their status as individuals within whom the stuff of heaven now resides. Walking among the un-spirited-people, those who have received the spirit of truth will be distinguishable by a higher and nobler quality within - a character filled with the spirit of truth.
This causes all sorts of trouble for those who are spirit-of-truth receivers, for they now face the frustration (at the least) and blatant opposition (at the worst) of conducting themselves as people of the spirit in a world which neither recognizes it at work, nor understands it in concept. Therein lies the state of our world, divided between the spirit of truth (the Spirit of God) and those who have never been released from the plane of earth. To anticipate the coming of the spirit of truth is always portrayed in Christian circles as such a happy moment, seldom counting the cost of what division will be placed between the receiver and the ignorer.
Understanding this moves us closer to living the faith to which we have been summoned by the very spirit of truth that is at work in all of this.